:',34 Sir J. Dewar and Mr. R. A. Hadfield. Effect of [Nov. 24, 



It is curious to find that by chilling down the metals iron, nickel, and 

 copper to - 182 C. their absolute and ultimate if the terms may be 

 allowed qualities are shown more truly than at the normal tempera- 

 ture. The effects here noticed also explain in a more satisfactory 

 manner than has yet been possible, why nickel is so valuable in nickel- 

 iron alloys ; that is, it tends to counteract the constant tendency of the 

 sensitive metal, iron, to become embrittled on the slightest provocation. 

 If this research reveals this one important fact, it will have well repaid 

 the labour. 



From the results it would seem to be indicated that copper might be 

 a useful metal to alloy with iron. There are, however, difficulties in 

 the way of this, at any rate as regards forged metal, as copper-iron 

 alloys containing no manganese are considerably red-short, and cannot 

 be readily manipulated. For some reason not yet explained it also 

 does not alloy well with iron, but this may be a question of temperature 

 effect at fusion point. At any rate, these experiments are suggestive 

 for further research and investigation. 



In the case of aluminium, Test No. 113 (Al 99*50 per cent.), the 

 metal shows a remarkable increase in tenacity, viz., 8 to 15 tons, the 

 elongation being nearly quadrupled, viz., from 7 to 27 per cent. 

 Singularly enough, when alloyed with iron, such increases in both 

 tenacity and ductility are not noticed; in fact, a contrary effect 

 was produced. 



Specimens of cupro-nickel (Cu 95, Ni 4 '85 per cent.) and Bull's 

 metal showed only slight changes at low temperature, whilst specimens 

 of delta metal and manganese copper showed a rise in tenacity and 

 ductility. 



Various experiments carried out in connection with this research deal 

 with contraction, electrical properties, micro-structure, magnetic and 

 brittleness tests, all of which will be included in the special mono- 

 graph. 



General Conclusions. 



It is clear that as regards iron and iron alloys, with, however, 

 certain exceptions, the effect of low temperature is to increase in a 

 remarkable degree their maximum tensile stress, and to reduce their 

 ductility to practically nothing. These changes take place to the same 

 extent, and this is very curious in the softest wrought iron, as 

 represented by the specimens S.C.I. (Swedish charcoal iron), L.S.S. 

 (the famous Swedish melting iron), and also English wrought iron, and 

 in carbon steel samples from (HO to 0'20 per cent, to the high percentages, 

 such as 1-25 or 1'50 per cent. Thus, the absence or presence of carbon 

 in ordinary carbon steel, in which other special elements are not 

 present, seems to have but little influence. That there is no error in 

 this statement is proved, independently of the tensile tests, by the fact 

 that several bars of the S.C.I., and mild steel specimens, were sub- 



